Human neutrophil elastase (HNE) is a 32 kDa serine proteinase found in the azurophilic granules of neutrophils. It has a role in the degradation of a wide range of extracellular matrix proteins, including fibronectin, laminin, proteoglycans, Type III and Type IV collagens as well as elastin (Bieth, G. In Regulation of Matrix accumulation, Mecham, R. P. (Eds), Academic Press, NY, USA 1986, 217-306). HNE has long been considered to play an important role in homeostasis through repair and disposal of damaged tissues via degradation of the tissue structural proteins. It is also relevant in the defence against bacterial invasion by means of degradation of the bacterial body. In addition to its effects on matrix tissues, HNE has been implicated in the upregulation of IL-8 gene expression and also induces IL-8 release from the epithelial cells of the lung. In animal models of Chronic Obstructive Pulmonary Disease induced by tobacco smoke exposure both small molecule inhibitors and protein inhibitors of HNE inhibit the inflammatory response and the development of emphysema (Wright, J. L. et al. Am. J. Respir. Crit. Care Med. 2002, 166, 954-960; Churg, A. et al. Am. J. Respir. Crit. Care Med. 2003, 168, 199-207). Thus, HNE may play a role both in matrix destruction and in amplifying inflammatory responses in chronic respiratory diseases where neutrophil influx is a characteristic feature. Indeed, HNE is believed to play a role in several pulmonary diseases, including chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), acute respiratory distress syndrome (ARDS), pulmonary emphysema, pneumonia and lung fibrosis. It is also implicated in several cardiovascular diseases in which tissue remodelling is involved, for example, in heart failure and the generation of ischaemic tissue injury following acute myocardial infarction.
COPD is an umbrella term encompassing three different pathological conditions, all of which contribute to limitation of airflow: chronic bronchitis, emphysema and small-airway disease. Generally all three will exist to varying extents in patients presenting with COPD, and all three may be due to neutrophil-mediated inflammation, as supported by the increased number of neutrophils observed in bronchoalveolar leakage (BAL) fluids of COPD patients (Thompson, A. B.; Daughton, D.; et al. Am. Rev. Respir. Dis. 1989, 140, 1527-1537). The major pathogenic determinant in COPD has long been considered to be the protease-anti-protease balance (also known as the ‘elastase:anti-elastase hypothesis’), in which an imbalance of HNE and endogenous antiproteases such as α1-antitrypsin (α1-AT), Secretory leukocyte protease inhibitor (SLPI) and pre-elafin leads to the various inflammatory disorders of COPD. Individuals that have a genetic deficiency of the protease inhibitor a 1-antitrypsin develop emphysema that increases in severity over time (Laurrell, C. B.; Erikkson, S Scand. J. Clin. Invest. 1963 15, 132-140). An excess of HNE is therefore destructive, leading to the breakdown of pulmonary morphology with loss of elasticity and destruction of alveolar attachments of airways in the lung (emphysema) whilst simultaneously increasing microvascular permeability and mucus hypersecretion (chronic bronchitis).
International patent publication WO2007/129060 relates, inter alia, to homodimeric or heterodimeric compounds of formula M-L-M1 wherein L is a divalent linker radical and M and M1 are each independently a radical of formula (A′) or (B′):
wherein
A is aryl or heteroaryl;
D is oxygen or sulphur;
R1, R2, R3 and R5 are independently each hydrogen, halogen, nitro, cyano, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, hydroxy or C1-C6-alkoxy or C2-C6-alkenyloxy, wherein C1-C6-alkyl and C1-C6-alkoxy can be further substituted with one to three identical or different radicals selected from the group consisting of halogen, hydroxy and C1-C4-alkoxy;
R and R4 each independently represent a radical of formula —[X]m—[Alk1]p-[Q]n-[Alk2]q-[X1]k-Z wherein
k, m, n, p and q are independently 0 or 1;
Alk1 and Alk2 each independently represent an optionally substituted C1-C6 alkylene, or C2-C6 alkenylene radical which may optionally contain an ether (—O—), thioether (—S—) or amino (—NRA—) link wherein RA is hydrogen or C1-C3 alkyl;
Q represents (i) —O—, —S—, —S(═O)—, —S(═O)2—, —S+(RA)—, —N(RA)—, —N+(RA)(RB)—, —C(═O)—, —C(═O)O—, —OC(═O)—, —C(═O)NRA—, —NRAC(═O)—, —S(O2)NRA—, —NRAS(O2)—, —NRAC(═O)NRB—, —NRAC(═NRA)NRB—, —C(═NRD)NRE—, —NREC(═NRD)—,
wherein RA, RB, RD and RE are independently hydrogen, C1-C6 alkyl, or C3-C6 cycloalkyl, or RA and RB, or RD and RE taken together with the nitrogen to which they are attached form a monocyclic heterocyclic ring of 5 to 7 ring atoms which my contain a further heteroatom selected from N, O and S, or (ii) an optionally substituted divalent mono- or bicyclic carbocyclic or heterocyclic radical having 3-6 ring members;
X represents —(C═O)—, —S(O2)—, —C(═O)O—, —(C═O)NRA—, or —S(O2)NRA—, wherein RA is hydrogen, C1-C6 alkyl, or C3-C6 cycloalkyl;
X1 represents —O—, —S—, or —NH; and
Z is hydrogen or an optionally substituted mono- or bicyclic carbocyclic or heterocyclic radical having 3-6 ring members.